Method and apparatus for uplink channel accessing wireless communication system

ABSTRACT

A communication technique for fusing 5G communication, which supports a higher data transmission rate than a 4G system, with an IoT technology is provided, and may be applied to an intelligent service based on the 5G communication technology and the IoT related technology. Accordingly, a method for transmitting information by a base station in a wireless communication system, includes generating information on a channel sensing operation of a user equipment (UE) in an unlicensed band, wherein the information on the channel sensing operation indicates one of a first type performing the channel sensing operation using a variable time period, a second type performing the channel sensing operation using a fixed time period, and a third type not performing the channel sensing operation; and transmitting, to the UE, the information on the channel sensing operation.

PRIORITY

This application is a Continuation Application of U.S. patentapplication Ser. No. 15/448,218, which was filed in the U.S. Patent andTrademark Office on Mar. 2, 2017, and claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application Ser. No. 62/302,489, which wasfiled on Mar. 2, 2016, and to U.S. Provisional Application Ser. No.62/373,521, which was filed on Aug. 11, 2016, the entire disclosure ofeach of these applications is incorporated herein by reference.

BACKGROUND 1. Field of the Disclosure

The present disclosure relates to a channel sensing method, and moreparticularly, to a channel access method including a channel sensingoperation and a channel occupation operation that are performed by atransmitting node or a receiving node for uplink signal transmission ina wireless communication system using an unlicensed band.

2. Description of the Related Art

To meet a demand for radio data traffic that is on an increasing trendsince commercialization of a 4G communication system, efforts to developan improved 5G communication system or a pre-5G communication systemhave been conducted. For this reason, 5G communication systems or thepre-5G communication systems can be called a beyond 4G networkcommunication system or a post LTE system.

To achieve a high data transmission rate, the 5G communication system isconsidered to be implemented in a super high frequency (mmWave) band(e.g., a 60 GHz band). To relieve a path loss of a radio wave andincrease a transfer distance of a radio wave in the super high frequencyband, in the 5G communication system, technologies such as beamforming,massive multi-input multi-output (MIMO), full dimensional MIMO(FD-MIMO), an array antenna, analog beam-forming, and a large scaleantenna have been used. Further, to improve a network of the system, inthe 5G communication system, technologies such as an evolved small cell,an advanced small cell, a cloud radio access network (RAN), anultra-dense network, a device to device communication (D2D), a wirelessbackhaul, a moving network, cooperative communication, coordinatedmulti-points (CoMP), and interference cancellation have been developed.In addition, in the 5G system, hybrid frequency shift keying (FSK) andquadrature amplitude modulation (QAM) modulation (FQAM) and slidingwindow superposition coding (SWSC), which are an advanced codingmodulation (ACM) scheme and a filter bank multi carrier (FBMC), anon-orthogonal multiple access (NOMA), and a sparse code multiple access(SCMA) that are an advanced access technology, and so on have beendeveloped.

Meanwhile, the Internet has evolved from in a human-centered connectionnetwork through which a human being generates and consumes informationto an internet of things (IoT) network that transmits and receivesinformation between distributed components such as things and processesthe information. The internet of everything (IoE) technology in whichthe big data processing technology is combined with the IoT technologyby connection with a cloud server has also emerged. To implement theIoT, technology elements, such as a sensing technology, wired andwireless communication and network infrastructure, a service interfacetechnology, and a security technology, have been required. Recently,technologies such as a sensor network, machine to machine (M2M), andmachine type communication (MTC) for connecting between things has beenresearched. In the IoT environment, an intelligent internet technology(IT) service that creates a new value in human life by collecting andanalyzing data generated in the connected things may be provided. TheIoT may be applied to fields, such as a smart home, a smart building, asmart city, a smart car or a connected car, a smart grid, health care,smart appliances, and an advanced healthcare service, by fusing andcombining the existing information technology with various industries.

Therefore, various attempts to apply the 5G communication system to theIoT network have been conducted. For example, the 5G communicationtechnologies, such as the sensor network, the M2M, and the MTC, havebeen implemented by techniques such as beamforming, MIMO, and the arrayantenna. An example of the application of the cloud radio access network(cloud RAN) as the big data processing technology described above mayalso be the fusing of 5G technology with the IoT technology.

To meet a demand for wireless data traffic, discussions are underway todevelop communication methods in various fields. For example, there areuser equipment (UE) to UE communication, a frequency integration systemfor operating a plurality of cells, and a multi-antenna system using alarge-scale antenna, or the like.

In recent years, a wireless communication system has been developed as ahigh-speed and high-quality wireless packet data communication system toprovide a data service and a multimedia service in addition to provisionof early voice-oriented service. In order to support the high-speed andhigh quality wireless packet data transmission service, various wirelesscommunication standards such as high speed downlink packet access(HSDPA), high speed uplink packet access (HSUPA), long term evolution(LTE), long term evolution advanced (LTE-A) of 3rd generationpartnership project (3GPP), high rate packet data (HRPD) of 3GPP2, and802.16 of Institute of Electrical and Electronics Engineers (IEEE) havebeen developed. In particular, the LTE/LTE-A (LTE) has been continuouslydeveloped and progressed to improve system throughput and frequencyefficiency. Typically, in the case of the LTE system, data transmissionrate and system throughput may be significantly increased by using afrequency integration technology (carrier aggregation, (CA)) capable ofoperating the system using a plurality of frequency spectra. However,the frequency spectrum in which the LTE system currently operates is alicensed band or licensed carrier that an operator may use with its ownauthority. When a frequency spectrum (e.g., 5 GHz or less) in which thewireless communication service is typically provided, since it isalready occupied and used by other operators or other communicationsystems, it may be difficult for the operator to secure a plurality oflicensed band frequencies. Therefore, it is difficult to increase thesystem throughput using the CA technology. Accordingly, in order toprocess increasing mobile data in a situation in which it is hard tosecure the licensed band frequency as described above, recently, atechnology for utilizing the LTE system in an unlicensed band orunlicensed carrier has been researched (e.g., LTE in unlicensed (LTE-U)and licensed-assisted access (LAA)). Among the unlicensed spectra,particularly, 5 GHz spectrum is used by the relatively smaller number ofcommunication devices as compared to 2.4 GHz unlicensed band, and mayutilize significantly wide bandwidth, thus it is relatively easy tosecure additional frequency spectrum. In other words, the licensed bandfrequency and the unlicensed band frequency may be utilized by using theLTE technology aggregating and using a plurality of frequency spectra,that is, the CA technology. In other words, an LTE cell in a licensedband may be set as PCell (or Pcell), an LTE in an unlicensed band (LAAcell or LTE-U cell) may be set as SCell (or Scell), such that the LTEsystem may be operated in the licensed band and the unlicensed bandusing the existing CA technology. The system may also be applied to adual-connectivity environment, in which the licensed band and theunlicensed band are connected by a non-ideal backhaul, as well as theCA, in which the licensed band and the unlicensed band are connected byan ideal backhaul. However, in the present disclosure, the descriptionwill be made under the assumption of the CA environment in which thelicensed band and the unlicensed band are connected by an idealbackhaul.

Generally, the LTE/LTE-A system is a method of transmitting data byusing an orthogonal frequency division multiple access (OFDM)transmission scheme. In the OFDM scheme, a modulation signal ispositioned at a two-dimensional resource configured of a time and afrequency. Resources on a time-axis are distinguished from each other bydifferent OFDM symbols, and are orthogonal to each other. Resources on afrequency-axis are distinguished from each other by differentsub-carriers, and are also orthogonal to each other. That is, in theOFDM scheme, when a specific OFDM symbol on the time-axis is designatedand a specific sub-carrier on the frequency-axis is designated, oneminimum unit resource may be indicated. The indicated minimum unitresource can be referred to as a resource element (RE). Different REsare orthogonal to each other even after passing through a frequencyselective channel, therefore signals transmitted through different REsmay be received by a reception side without causing interference witheach other. In the OFDM communication system, a downlink bandwidthincludes a plurality of resource blocks (RB), and each physical resourceblock (PRB) may include 12 sub-carriers arranged along thefrequency-axis and 14 or 12 OFDM symbols arranged along the time-axis.Here, the PRB can be a basic unit for resource allocation.

A reference signal (RS) that is received from a base station, is asignal allowing a terminal to estimate a channel. In an LTEcommunication system, a demodulation reference signal (DMRS) can beincluded as one of a common reference signal (CRS) and an exclusivereference signal. A CRS that is a reference signal transmitted acrossentire downlink bandwidth, may be received by all terminals, and can beused in channel estimation, feedback information configuration of theterminal, or demodulation of a control channel and a data channel. ADMRS that is also a reference signal transmitted across entire downlinkbandwidth, can be used in data channel modulation and channel estimationof a specific terminal, but is not used in feedback informationconfiguration, unlike the CRS. Therefore, The DMRS can be transmittedthrough the PRB resource to be scheduled by the terminal.

On the time-axis, a subframe includes two slots, a first slot and asecond slot, each having a length of 0.5 msec. A physical dedicatedcontrol channel (PDCCH) region that is a control channel region and anenhanced PDCCH (ePDCCH) region that is a data channel region are dividedon the time-axis and then transmitted. This is to rapidly receive anddemodulate the control channel signal. In addition, the PDCCH region ispositioned across the entire downlink spectrum and has a form in whichone control channel is divided into small units of control channels tobe dispersed in the entire downlink spectrum. An uplink is largelydivided into a control channel (PUCCH) and a data channel (PUSCH), and aresponse channel for the downlink data channel and other feedbackinformation are transmitted through the control channel when the datachannel is not present, and are transmitted through the data channelwhen the data channel is present.

FIGS. 1A and 1B are diagrams illustrating a conventional communicationsystem to which the present disclosure can be applied.

Referring to FIGS. 1A and 1B, FIG. 1A illustrates a case in which an LTEcell 102 and an LAA cell 103 coexist in one small base station 101 in anetwork, and a terminal 104 performs transmission and reception of datawith the base station 101 through the LTE cell 102 and the LAA cell 103.Schemes other than a duplex scheme of the LTE cell 102 or the LAA cell103 can also be used. A cell performing data transmission and datareception by using a licensed band may be assumed as the LTE cell 102 orPCell, and a cell performing data transmission and data reception byusing an unlicensed band may be assumed as the LAA cell 103 or SCell.However, when the LTE cell is PCell, uplink transmission may beperformed only through the LTE cell 102.

FIG. 1B illustrates a case in which an LTE macro base station 111 forachieving wide coverage in the network and an LAA small base station 112for increasing data transmission amount are installed; schemes otherthan a duplex scheme of the LTE macro base station 111 or the LAA smallbase station may also be used. In this case, the LTE macro base station111 may also be replaced by an LTE small base station. Further, when theLTE base station is PCell, uplink transmission may be performed onlythrough the LTE base station 111. The LTE base station 111 and the LAAbase station 112 can be assumed to have an ideal backhaul network.Accordingly, fast X2 communication (or interface) 113 between the basestations is possible, such that even when the uplink transmission isperformed only through the LTE base station 111, the LAA base station112 may receive relevant control information from the LTE base station111 through the X2 communication 113 in real time. Methods in accordancewith the present disclosure may be applied to both of the systems inFIG. 1A and FIG. 1B.

In general, the unlicensed band is used in a manner that a plurality ofdevices share the same frequency spectrum or channel. The devices usingthe unlicensed band may be systems different from each other. Therefore,general operation of the devices operated in the unlicensed band forcoexistence of various devices is as follows.

A transmitting device requiring transmission of a signal including adata signal, a control signal, or the like, confirms, with respect tothe unlicensed band or a channel in which the signal transmission isperformed, channel occupancy state of other devices before performingthe signal transmission, and may occupy the channel depending on thedetermined channel occupancy state. The operation as described above isgenerally called listen-before-talk (LBT). In other words, thetransmitting device needs to determine whether the transmitting devicemay occupy the channel according to a predefined or preset method. Amethod for sensing the channel may be defined or set in advance.Further, the time for sensing the channel may be defined or set inadvance or randomly selected within a specific range. Moreover, thechannel sensing time may be set in proportion to a set maximum channeloccupancy time. A channel sensing operation for determining whether thechannel may be occupied as described above may be set to be differentdepending on an unlicensed frequency spectrum in which the operation isperformed, or regional and national regulation. For example, currently,in the United States, the unlicensed band may be used without a separatechannel sensing operation except an operation for radar sensing in afrequency spectrum of 5 GHz.

The transmitting devices to use the unlicensed band may sense whetherother devices use the corresponding channel through the foregoingchannel sensing operation (or LBT) as described above, and use thechannel by occupying the channel when it is sensed that the channel isnot occupied by other devices in the channel. The devices using theunlicensed band may operate by defming or setting a maximum channeloccupancy time for which the devices may continuously occupy a channelafter the channel sensing operation, in advance. The maximum channeloccupancy time may be defined in advance according to regulation definedin accordance with a frequency spectrum, a region, or the like, or maybe separately set by a base station in a case of other devices, e.g., aterminal. The channel occupancy time may be set to be differentdepending on an unlicensed band or regional and national regulations.For example, in Japan, the maximum channel occupancy time is set to 4 msin the unlicensed band of 5 GHz. Meanwhile, in Europe, the continuouschannel occupancy time may be set to 10 ms or 13 ms. The devicesoccupying the channel for the maximum channel occupancy time may performthe channel sensing operation again, and then reoccupy the channelaccording to the channel sensing result.

The channel sensing operation and the channel occupation operation inthe unlicensed band as described above will be described below withreference to FIG. 2, which illustrates a downlink transmission processof transmitting, by the base station, data or control signal to theterminal as an example, and the process may also be applied to uplinktransmission in which the terminal transmits a signal to the basestation.

An LTE subframe 200 in FIG. 2 is a subframe having a length of 1 ms, andmay be configured of a plurality of OFDM symbols. The base station andthe terminal capable of performing communication using an unlicensedband may perform communication by occupying a corresponding channelduring a set channel occupancy time 250 and 260. When the base stationoccupying the channel for the set channel occupancy time 250 needs toadditionally occupy the channel, the base station may perform thechannel sensing operation 220, and then may reoccupy and use the channeldepending on a result of the channel sensing operation. The requiredchannel sensing period (or length) may be defined between the basestation and the terminal in advance, set through a higher layer signaltransmitted by the base station for the terminal, or set to be differentaccording to a transmission/reception result of data transmitted throughthe unlicensed band.

Further, at least one of variables applied to the channel sensingoperation that is performed again as described above may be set to bedifferent from those of the previous channel sensing operation.

The operation for sensing and occupying a channel may be set to bedifferent depending on the unlicensed band or regional and nationalregulations. The operation for sensing and occupying a channel withrespect to a load-based equipment, which is one of channel accessmethods in EN301 893, a rule for 5 GHz spectrum of Europe, will bedescribed in more detail below.

When the base station needs to additionally use the channel after themaximum channel occupancy time 250, it is required to determine whetherother devices occupy the channel during a minimum channel sensing period220. The minimum channel sensing period 220 may be set with a, dependingon the maximum channel occupancy period, maximum channel occupancyperiod of 13/32×q, (q=4, . . . , 32) and a minimum channel sensingperiod of length of extended clear channel assessment (ECCA) slot x rand(1, q).

Here, the length of the ECCA slot is a predefined or preset minimum unit(or length) of the channel sensing period. That is, when q is set to 32,the transmitting device may occupy the unlicensed band for up to 13 ms.A minimum channel sensing period, a random value from 1 to q (that is, 1to 32), may be selected, and a total channel sensing period may be thelength of the ECCA slot x of the selected random value. Therefore, whenthe maximum channel occupancy period is increased, the minimum channelsensing period can also be increased. The method for setting the maximumchannel occupancy period and the minimum channel sensing period ismerely an example, may be applied differently depending on the frequencyspectrum, and the defined regional and national regulations, and may bechanged depending on frequency regulation amendments still to bedetermined. Further, an additional operation (e.g., introduction ofadditional channel sensing period) in addition to the channel sensingoperation according to the frequency regulation may also be included.

When other devices using the corresponding unlicensed band is not sensedby the base station in the channel sensing period 220, that is, when thechannel is determined to be in an idle state, the base station mayimmediately occupy and use the channel. The determination on whetherother devices occupy the channel in the channel sensing period 220 maybe performed using a predefined or preset reference value. For example,when intensity of a signal received from other devices during thechannel sensing period is greater than a predetermined reference value(e.g., −62 dBm), it may be determined that the channel is occupied byother devices. When the intensity of the received signal is smaller thana reference value, the channel may be determined to be in the idlestate. The method for determining whether the channel is occupied mayinclude various methods such as the foregoing method using the size ofthe reception signal, a method of detecting a signal defined in advance,or the like.

Since a general LTE operation is performed in a subframe unit, thesignal may not be transmitted or received in the specific OFDM symbolimmediately after performing the channel sensing operation (e.g., asignal transmission and reception operation is performed from a firstOFDM symbol of the subframe). Therefore, the base station sensing theidle channel in the channel sensing period 220 in the subframe asdescribed above may transmit a specific signal 230 for channel occupancyfrom the point in time when the channel sensing period 220 ends toimmediately before first OFDM symbol transmission of a next subframe,i.e., during a period 230. In other words, the base station may transmita second signal (e.g., primary synchronization signal (PSS)/secondarysynchronization signal (SSS)/cell-specific reference signal (CRS), anewly defined signal, etc.) for channel occupancy with respect tocorresponding unlicensed band, synchronization of the terminal, etc.,before transmitting a first signal (e.g., general ePDCCH and PDSCH)transmitted in the subframe 210 or 240. The transmitted second signalmay not be transmitted depending on the channel sensing period endingpoint in time. Further, when a corresponding channel occupancy startingpoint in time is set within the specific OFDM symbol, a third signal (anewly defined signal) is transmitted to a next OFDM symbol startingpoint in time, and the second signal or the first signal may betransmitted. In the present disclosure, the channel sensing operationperiod is described using an OFDM symbol unit, but the channel sensingoperation period may be set regardless of the OFDM symbol of the LTEsystem.

Here, the PSS/SSS currently used in the LTE system may be reused as thesecond signal, or the second signal may be generated using at least oneof the PSS and the SSS by using root sequence currently used in thelicensed band and other sequence. Further, the second signal may begenerated using other sequences except the PSS/SSS sequence required togenerate a physical cell ID (PCID) of the base station in the unlicensedband to be used without being confused with the physical cell ID of thebase station. Further, the second signal includes at least one of CRSand CSI-RS currently used in the LTE system, or ePDCCH, PDSCH, or asignal having modified form of ePDCCH and PDSCH may be used as thesecond signal.

Since the period 230 in which the second signal is transmitted isincluded in the channel occupancy time, frequency efficiency may bemaximized by allowing minimum information to be transmitted through thesecond signal transmitted in the period 230.

The LTE system (LAA or LAA cell) using the unlicensed band as describedabove requires a new channel access (or LBT) scheme that is differentfrom the existing method of using the licensed band, in order to satisfyregulations on the unlicensed band to be used and coexist with othersystems (wireless-fidelity (WiFi)) using the unlicensed band.

Referring to FIG. 3, the channel access scheme for using the unlicensedband of the WiFi system is now described.

When a WiFi AP1 310 has data to be transmitted to station 1 (STA1) or aterminal 1 315, a channel sensing operation for a corresponding channelcan be performed to occupy the channel. Generally the channel is sensedduring distributed coordination function (DCF) interframe space (DIFS)time 330. Whether the channel is occupied by other devices may bedetermined by various methods, e.g., using intensity of the signalreceived during the time 330, a method of detecting a signal defined inadvance, or the like. When it is determined that the channel is occupiedby another device 320 during the channel sensing time 330, the AP1 310selects a random variable 355, e.g., N in a set contention window (e.g.,1-16). Generally, such operation is called a backoff operation. Then,the AP1 310 senses the channel during a predefined time (e.g., 9 us),and when it is determined that the channel is in the idle state, theselected variable N 355 can be subtracted by 1. That is, it is updatedas N=N−1. When it is determined that the channel is occupied by theanother device 320 during the time 330, the variable N 355 is notsubtracted but is instead frozen. STA2 325 receives data 340 transmittedby the AP2 320 and transmits ACK or NACK 347 with respect to thereception of the data 340 to the AP2 320 after short interframe space(SIFS) time 345. The STA2 325 may transmit the ACK/NACK 347 withoutperforming a separate channel sensing operation. After the transmissionof the ACK 347 of the STA2 325 ends, the AP1 310 may know that thechannel is in the idle state. The API 310 senses the channel during apredetermined time (e.g., 9 us) defined or set in advance for thebackoff operation when it is determined that the channel is in the idlestate for the DIFS time 350, and when it is determined that the channelis in the idle state, the selected variable N 355 is subtracted again.That is, it is updated as N=N−1. When N=0, the AP1 310 may occupy thechannel to transmit the data 360 to the STA 1 315. Then, the terminalreceiving the data 360 may transmit the ACK or NACK with respect to thereception of the data to the AP1 310 after the SIFS time. The AP1 310receiving the NACK from the STA1 315 may select the random variable Nused in the next backoff operation in the increased contention window.That is, when it is assumed that the contention window used is [1, 16],and the data reception result of the STA1 315 is NACK, the contentionwindow of the AP1 310 receiving the NACK may be increased to [1, 32]. Ifthe AP1 310 receives ACK in the above case, the contention window may beset to an initial value (e.g., [1, 16]) or a preset contention windowmay be decreased or maintained.

However, with a WiFi system, communication is generally performedbetween one AP (or base station) and one STA (or terminal) at the sametime. Further, as 347 and 370 in FIG. 3, the STA1 and STA2 (or terminals315, 325) transmits its data reception state (e.g., ACK or NACK) to theAP (or base station) immediately after the reception of the data. The AP310 or 320 performs a channel sensing operation for the next datatransmission operation after receiving ACK or NACK from the terminal 315or 325. However, in the LAA system, one base station may transmit datato a plurality of terminals at the same time. Further, one or moreterminals receiving the data at the same point in time (e.g., time n)may transmit ACK or NACK to the base station at the same time (e.g., n+4in a case of FDD). Therefore, the LAA base station may receive the ACKor NACK from one or more terminals at the same point in time, unlike theWiFi system. In addition, time difference between the ACK/NACKtransmission point in time of the terminal and the data transmissiontime of the base station may be at least 4 ms. Therefore, of the LAAbase station sets (or resets) a contention window by the ACK/NACKreceived from the terminal like WiFi, since the base station may receivethe ACK/NACK from a plurality of terminals at a specific time,uncertainty in setting the contention window may occur. Further, if theterminal performs an uplink channel sensing operation for uplinktransmission, each terminal may independently perform the channelsensing operation. When the terminal independently performs the channelsensing operation as described above, only a terminal of which thechannel sensing operation ends first may perform the set uplinktransmission.

Accordingly, the present disclosure provides a method in which the basestation sets a channel sensing period based on the uplink signalreception result received from the terminal, and performs a setting ofthe set channel sensing period for terminals such that the plurality ofterminals may perform the channel sensing operation at the same time.

SUMMARY

Accordingly, an aspect of the present disclosure provides a method andan apparatus for setting a channel sensing period for an unlicensedband.

An aspect of the present disclosure provides that when performing achannel occupation operation in an unlicensed band, at least one ofvariables for the channel occupation operation is set by using a datareception result transmitted using the unlicensed band.

In accordance with an aspect of the present disclosure, there isprovided a base station for transmitting information in a wirelesscommunication system. The base station includes a transceiver; and acontroller coupled with the transceiver and configured to control togenerate information on a channel sensing operation of a user equipment(UE) in an unlicensed band, wherein the information on the channelsensing operation indicates one of a first type performing the channelsensing operation using a variable time period, a second type performingthe channel sensing operation using a fixed time period, and a thirdtype not performing the channel sensing operation, and transmit, to theUE, the information on the channel sensing operation.

In accordance with another aspect of the present disclosure, there isprovided a method for transmitting information by a base station in awireless communication system. The method includes generatinginformation on a channel sensing operation of a user equipment (UE) inan unlicensed band, wherein the information on the channel sensingoperation indicates one of a first type performing the channel sensingoperation using a variable time period, a second type performing thechannel sensing operation using a fixed time period, and a third typenot performing the channel sensing operation; and transmitting, to theUE, the information on the channel sensing operation.

In accordance with another aspect of the present disclosure, there isprovided a UE for receiving information in a wireless communicationsystem. The UE includes a transceiver; and a controller coupled with thetransceiver and configured to control to receive, from a base station,information on a channel sensing operation of the UE in an unlicensedband, wherein the information on the channel sensing operation indicatesone of a first type performing the channel sensing operation using avariable time period, a second type performing the channel sensingoperation using a fixed time period, and a third type not performing thechannel sensing operation, and transmit an uplink signal based on theinformation on the channel sensing operation.

In accordance with another aspect of the present disclosure, there isprovided a method for receiving information by a UE in a wirelesscommunication system. The method includes receiving, from a basestation, information on a channel sensing operation of the UE in anunlicensed band, wherein the information on the channel sensingoperation indicates one of a first type performing the channel sensingoperation using a variable time period, a second type performing thechannel sensing operation using a fixed time period, and a third typenot performing the channel sensing operation; and transmitting an uplinksignal based on the information on the channel sensing operation.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainembodiments of the present disclosure will be more apparent from thefollowing detailed description taken in conjunction with theaccompanying drawings, in which:

FIGS. 1A and 1B are diagrams illustrating a conventional communicationsystem;

FIG. 2 is a diagram illustrating a channel occupation operation based ona channel sensing operation;

FIG. 3 is a diagram illustrating a channel access scheme for anunlicensed band of a WiFi system;

FIG. 4 is a flowchart of a method for a channel access scheme for anunlicensed band of an LAA system, according to an embodiment of thepresent disclosure;

FIG. 5 is a diagram of a method for performing a channel sensingoperation, according to an embodiment of the present disclosure;

FIG. 6 is a diagram of a method for setting a contention window and achannel sensing period, according to an embodiment of the presentdisclosure;

FIG. 7 is a flowchart of a method for setting a contention window in abase station for a channel sensing operation, according to an embodimentof the present disclosure;

FIG. 8 is a flowchart of a method for setting a contention window in aterminal for a channel sensing operation, according to an embodiment ofthe present disclosure;

FIG. 9 is a diagram of a base station apparatus, according to anembodiment of the present disclosure; and

FIG. 10 is a diagram illustrating of a terminal apparatus, according toan embodiments of the present disclosure.

DETAILED DESCRIPTION

Embodiments of the present disclosure will be described herein belowwith reference to the accompanying drawings. However, the embodiments ofthe present disclosure are not limited to the specific embodiments andshould be construed as including all modifications, changes, equivalentdevices and methods, and/or alternative embodiments of the presentdisclosure.

The terms “have,” “may have,” “include,” and “may include” as usedherein indicate the presence of corresponding features (for example,elements such as numerical values, functions, operations, or parts), anddo not preclude the presence of additional features.

The terms “A or B,” “at least one of A or/and B,” or “one or more of Aor/and B” as used herein include all possible combinations of itemsenumerated with them. For example, “A or B,” “at least one of A and B,”or “at least one of A or B” means (1) including at least one A, (2)including at least one B, or (3) including both at least one A and atleast one B.

The terms such as “first” and “second” as used herein may modify variouselements regardless of an order and/or importance of the correspondingelements, and do not limit the corresponding elements. These terms maybe used for the purpose of distinguishing one element from anotherelement. For example, a first user device and a second user device mayindicate different user devices regardless of the order or importance.For example, a first element may be referred to as a second elementwithout departing from the scope the present disclosure, and similarly,a second element may be referred to as a first element.

It will be understood that, when an element (for example, a firstelement) is “(operatively or communicatively) coupled with/to” or“connected to” another element (for example, a second element), theelement may be directly coupled with/to another element, and there maybe an intervening element (for example, a third element) between theelement and another element. To the contrary, it will be understoodthat, when an element (for example, a first element) is “directlycoupled with/to” or “directly connected to” another element (forexample, a second element), there is no intervening element (forexample, a third element) between the element and another element.

The expression “configured to (or set to)” as used herein may be usedinterchangeably with “suitable for,” “having the capacity to,” “designedto,” “ adapted to,” “made to,” or “capable of” according to a context.The term “configured to (set to)” does not necessarily mean“specifically designed to” in a hardware level. Instead, the expression“apparatus configured to . . . ” may mean that the apparatus is “capableof . . . ” along with other devices or parts in a certain context. Forexample, “a processor configured to (set to) perform A, B, and C” maymean a dedicated processor (e.g., an embedded processor) for performinga corresponding operation, or a generic-purpose processor (e.g., a CPUor an application processor) capable of performing a correspondingoperation by executing one or more software programs stored in a memorydevice.

The term “module” as used herein may be defined as, for example, a unitincluding one of hardware, software, and firmware or two or morecombinations thereof. The term “module” may be interchangeably usedwith, for example, the terms “unit”, “logic”, “logical block”,“component”, or “circuit”, and the like. The “module” may be a minimumunit of an integrated component or a part thereof. The “module” may be aminimum unit performing one or more functions or a part thereof. The“module” may be mechanically or electronically implemented. For example,the “module” may include at least one of an application-specificintegrated circuit (ASIC) chip, field-programmable gate arrays (FPGAs),or a programmable-logic device, which is well known or will be developedin the future, for performing certain operations.

The terms used in describing the various embodiments of the presentdisclosure are for the purpose of describing particular embodiments andare not intended to limit the present disclosure. As used herein, thesingular forms are intended to include the plural forms as well, unlessthe context clearly indicates otherwise. All of the terms used hereinincluding technical or scientific terms have the same meanings as thosegenerally understood by an ordinary skilled person in the related artunless they are defined otherwise. The terms defined in a generally useddictionary should be interpreted as having the same or similar meaningsas the contextual meanings of the relevant technology and should not beinterpreted as having ideal or exaggerated meanings unless they areclearly defined herein. According to circumstances, even the termsdefined in this disclosure should not be interpreted as excluding theembodiments of the present disclosure.

Electronic devices according to the embodiments of the presentdisclosure may include at least one of, for example, smart phones,tablet personal computers (PCs), mobile phones, video telephones,electronic book readers, desktop PCs, laptop PCs, netbook computers,workstations, servers, personal digital assistants (PDAs), portablemultimedia players (PMPs), Motion Picture Experts Group (MPEG-1 orMPEG-2) Audio Layer 3 (MP3) players, mobile medical devices, cameras, orwearable devices. According to an embodiment of the present disclosure,the wearable devices may include at least one of accessory-type wearabledevices (e.g., watches, rings, bracelets, anklets, necklaces, glasses,contact lenses, or head-mounted-devices (HMDs)), fabric or clothingintegral wearable devices (e.g., electronic clothes), body-mountedwearable devices (e.g., skin pads or tattoos), or implantable wearabledevices (e.g., implantable circuits).

The electronic devices may be smart home appliances. The smart homeappliances may include at least one of, for example, televisions (TVs),digital versatile disk (DVD) players, audios, refrigerators, airconditioners, cleaners, ovens, microwave ovens, washing machines, aircleaners, set-top boxes, home automation control panels, securitycontrol panels, TV boxes (e.g., Samsung HomeSync™, Apple TV™, or GoogleTV™), game consoles (e.g., Xbox™ and PlayStation™), electronicdictionaries, electronic keys, camcorders, or electronic picture frames.

The electronic devices may include at least one of various medicaldevices (e.g., various portable medical measurement devices (such asblood glucose meters, heart rate monitors, blood pressure monitors, orthermometers, and the like), a magnetic resonance angiography (MRA)device, a magnetic resonance imaging (MRI) device, a computed tomography(CT) device, scanners, or ultrasonic devices, and the like), navigationdevices, global positioning system (GPS) receivers, event data recorders(EDRs), flight data recorders (FDRs), vehicle infotainment devices,electronic equipment for vessels (e.g., navigation systems,gyrocompasses, and the like), avionics, security devices, head units forvehicles, industrial or home robots, automatic teller machines (ATMs),points of sales (POSs) devices, or Internet of things (IoT) devices(e.g., light bulbs, various sensors, electric or gas meters, sprinklerdevices, fire alarms, thermostats, street lamps, toasters, exerciseequipment, hot water tanks, heaters, boilers, and the like).

The electronic devices may further include at least one of parts offurniture or buildings/structures, electronic boards, electronicsignature receiving devices, projectors, or various measuringinstruments (such as water meters, electricity meters, gas meters, orwave meters, and the like). The electronic devices may be one or morecombinations of the above-mentioned devices. The electronic devices maybe flexible electronic devices. Also, the electronic devices are notlimited to the above-mentioned devices, and may include new electronicdevices according to the development of new technologies.

Hereinafter, the electronic devices according to various embodiments ofthe present disclosure will be described with reference to theaccompanying drawings. The term “user” as used herein may refer to aperson who uses an electronic device or may refer to a device (e.g., anartificial intelligence electronic device) which uses an electronicdevice.

According to the present disclosure, it is possible to improvecoexistence performance of a channel occupation operation betweendevices using an unlicensed band, thereby clearly setting a standard forthe channel occupation operation.

Although the present disclosure is described herein using an LTE systemand an LTE-A system, the present disclosure may be applied to othercommunication systems using a licensed band and an unlicensed band.

FIG. 4 is a flowchart of a channel access method for unlicensed band ofan LAA system, according to an embodiment of the present disclosure.

A channel occupancy method using an unlicensed band in an LAA systemwill be described with reference to FIG. 4. In step 401, an LAA cell (orLAA SCell, LAA Cell, LAA base station) that does not require datatransmission maintains an idle state. The idle state is a state in whichthe LAA cell does not transmit a data signal to an unlicensed band. Forexample, the idle is a state in which an LAA cell, in an active state,has no more data signal to be transmitted, or has data to be transmittedto the terminal but does not transmit the data to the terminal.

When it is required that the LAA cell, in the idle state, occupies achannel to transmit data or control signal to the terminal in step 402,the LAA cell may perform a first channel sensing operation or functionin step 403. The first channel sensing operation may be set to bedifferent depending on at least one condition of a preset time (e.g., 34us), a time set by other device, and a kind of data or control signal tobe transmitted in the LAA cell.

For example, a time for performing the first channel sensing operation,in a case in which the LAA cell only transmits the control signalwithout data transmitted to a specific terminal, may be set to bedifferent (e.g., when only transmitting the control signal, the firstchannel sensing operation is performed for a time shorter than that of acase of transmitting a data signal) from a time for performing the firstchannel sensing operation, in a case in which the LAA cell transmitsdata to the specific terminal.

Values that may be set for the first channel sensing operation may bedefined in advance. At least one of other variables (e.g., a thresholdvalue of an intensity of a received signal for determining whether thechannel is occupied) of the first channel sensing operation in additionto the time for performing the first channel sensing operation may beset to be different between the case in which the LAA cell onlytransmits the control signal without data transmitted to a specificterminal and the case in which the LAA cell transmits data to thespecific terminal.

The LAA cell may set a contention window used in a second channelsensing operation to an initial value. The first channel sensingoperation is an operation for determining whether other devices occupythe corresponding channel using various methods including at least oneof a method of measuring intensity of a received signal and a method ofdetecting a signal defined in advance, during the time set for the firstchannel sensing operation. The variables required for the first channelsensing operation including a time for performing the first channelsensing operation may use a preset value, or may be set by otherdevices.

When it is determined that the channel is in the idle state in step 404,the LAA cell may occupy the channel and transmit a signal in step 405.When it is determined that the channel is occupied by other devices instep 404, a random variable N may be selected in a contention window [x,y] set in step 407. An initial contention window may be set in advance(or may be reset) from the base station. Further, the set contentionwindow may be set using various values including the number of attemptsfor occupying the channel, occupancy rate for the cannel (e.g., trafficload), and a reception result (e.g., ACK/NACK) of the terminal for thedata signal transmitted at the time of occupying the channel.

When it is determined that the LAA cell occupying the channel in step405 needs to additionally occupy the channel in step 406, the contentionwindow may be set (reset) in step 414 using a result of datatransmission performed in step 405 or at least one of various methods asmentioned above. The method for setting the contention window using theresult of data transmission in step 405 is only one example, and thecontention window may be set by a previous channel occupancy and datatransmission step or a preset value.

When the LAA cell transmits data to the terminal in the channeloccupancy period and receives NACK as a reception result for the datatransmission from the terminal, the LAA cell may increase or maintainthe contention window. When the LAA cell occupying the channel using theincreased or maintained contention window transmits data to the terminalin the channel occupancy period and receives ACK as a reception resultfor the data transmission from the terminal, the LAA cell may decreaseor maintain the contention window or set the contention window as aninitial contention window. The method for setting a contention windowusing the ACK/NACK is merely an example, and the contention window maybe set using other reference values.

When the random variable N is set in the preset contention window instep 407, a second channel sensing operation may be performed using theset N in step 408. The second channel sensing operation is an operationfor determining whether the channel is occupied using at least one of amethod of measuring intensity of received signal and a method ofdetecting signal defined in advance, during a set time, anddetermination criteria different from that of the first sensingoperation may be set. That is, a time for performing the second channelsensing operation may be set to be the same as or shorter than that forperforming the first channel sensing operation. For example, the timefor performing the first channel sensing operation may be set to be 34us, and the time for performing the second channel sensing operation maybe set to be 9 us. Further, a reference threshold value of the secondchannel sensing operation may be set to be different from a referencethreshold value of the first channel sensing operation.

When it is determined that the channel sensed in step 408 is an idlechannel in step 409, 1 is subtracted from the set variable N in step410. A different value, however, may be subtracted depending on a setvalue, or the subtracted value may be set to be different depending on akind or characteristics of signals to be transmitted by the LAA cell.

When a subtracted value of the variable N is 0 in step 411, the LAA cellmay perform channel occupancy and data transmission in step 405. Whenthe value of the variable N is not 0 in step 411, the LAA cell mayperform the second channel sensing operation again in step 408. When itis determined that the channel is not the idle channel in step 408through the second channel sensing operation in step 409, the LAA cellmay perform a third channel sensing operation through step 412. Thethird channel sensing operation may be set identically to the firstchannel sensing operation or the second channel sensing operation. Forexample, both of a time for performing the first channel sensingoperation and a time for performing the third channel sensing operationmay be set to be 34 us. The reference threshold value of the firstchannel sensing operation may be set to be different from a referencethreshold value of the third channel sensing operation. The time forperforming the channel sensing operation and the threshold value aremerely examples, and variables or reference values required for thethird channel sensing operation may be set to be the same as those ofthe first channel sensing operation or at least one of them may be setto be different from those of the first channel sensing operation.

Further, the third channel sensing operation may be set to perform anoperation generating time delay without a separate operation for sensingor occupying the channel. The time for performing the third channelsensing operation may be set to be identical or different from at leastone of those for performing the first channel sensing operation or thesecond channel sensing operation. The LAA cell determines whether otherdevices occupy the channel in step 413 using the reference values setfor the third channel sensing operation. When the determined channeloccupancy state is the idle state, the second channel sensing operationmay be performed again in step 408. In a case in which the channeloccupancy state determined in step 413 is not the idle state, the LAAcell may perform the set third channel sensing operation in step 412. Atleast one of the first channel sensing operation, the second channelsensing operation, and the third channel sensing operation may beomitted depending on the type or characteristics of the data or controlsignal to be transmitted by the LAA cell.

When the LAA cell only transmits the control signal (e.g., discoveryreference signal (DRS)), the LAA cell may immediately occupy the channelafter performing only the first channel sensing operation according tothe result of the channel sensing operation. The DRS is merely anexample in which at least one of the first channel sensing operation,the second channel sensing operation, and the third channel sensingoperation may be omitted, and the DRS may also be applied at the time oftransmitting other control signal.

If the terminal performs an uplink channel occupancy or an uplinkchannel sensing operation for uplink transmission by the above describedchannel sensing method and the channel occupation method, each terminalmay independently perform the channel sensing operation. If the terminalindependently performs a channel sensing operation, each terminal has adifferent channel sensing period that is randomly selected in thecontention window as in step 407. Therefore, if a plurality of terminalsare scheduled in one uplink subframe, a terminal of which the channelsensing operation ends first among the terminals may start uplinktransmission first. Therefore, a terminal that is performing the channelsensing operation may not complete the channel sensing operation due toan uplink signal transmitted by the terminal. That is, in the abovecase, only the terminal of which the channel sensing operation endsfirst may perform the set uplink transmission.

Accordingly, the present disclosure proposes a method in which a basestation sets a channel sensing period based on the uplink signalreception result received from the terminal, and performs a setting ofthe set channel sensing period for terminals such that the plurality ofterminals may perform the channel sensing operation at the same time, inorder for the terminals of which uplink transmission is set in the samesubframe not to set different channel sensing periods from each other.

FIG. 5 is a diagram of a method for performing a channel sensingoperation, according to an embodiment of the present disclosure.

In view of an LAA cell and an LAA terminal receiving control and datasignals from the LAA cells, an uplink channel sensing operation and achannel access method of the LAA terminal will be described withreference to FIG. 5.

The LAA terminal may receive scheduling information for uplinktransmission in subframe n to subframe n+K from one cell of cellsoperating in an unlicensed band or a licensed band. K may be defined bythe base station and the terminal in advance or set by the base stationthrough a higher layer signal for the terminal, or the base station mayperform a setting of a time relation between an uplink transmissionsetting point in time and a start point in time of the set uplinktransmission for the terminal by including the K value in uplinktransmission setting information (for example, DCI format 0, 4, or DCIformat modified for newly introduced for setting uplink transmission).

For convenience of explanation, a case in which K=4 (ms) will be assumedand explained, but K may be set to a value greater than or equal to than1 ms. In order to minimize delay between the uplink transmission settingand actual uplink transmission, K may also be set in a unit less thanK=1 (ms).

If the set uplink signal transmission is uplink transmission for anunlicensed band, the terminal performs a channel sensing operationbefore performing the set uplink transmission, and if it is determinedthat the unlicensed band is in an idle state, the set uplinktransmission may be performed. If it is determined that the unlicensedband is occupied by other devices, the terminal may not perform the setuplink transmission.

When downlink transmission of the LAA cell is performed when the LAAterminal performs the channel sensing operation for the unlicensed band,the LAA terminal may determine that the channel is occupied by otherdevices due to a downlink signal of the LAA cell. Accordingly, the LAAcell and the LAA terminal may transmit no signal in the time andfrequency resources immediately before performing the unlinktransmission or when the LAA terminal performs the channel sensingoperation for the unlicensed band.

The channel sensing operation performed by the LAA terminal for anunlicensed band may be performed by using at least one of the followingmethods:

Method 1: Uplink signal transmission for a fixed time after sensing achannel for an unlicensed band;

Method 2: Uplink signal transmission for a variable time after sensing achannel for an unlicensed band; and

Method 3: Uplink signal transmission without sensing a channel.

With respect to Method 1, the LAA terminal of which uplink signaltransmission is set in an unlicensed band may perform a channel sensingoperation for the unlicensed band in which the uplink signaltransmission is set for a fixed channel sensing period 525 before theset uplink signal transmission. If a point in time when the channelsensing operation ends is earlier than the set uplink signaltransmission point in time, the terminal may transmit an occupancysignal 550 for occupying the channel from the point in time when thechannel sensing operation ends to the uplink signal transmission pointin time. If the channel sensing operation ends immediately before theuplink signal transmission point in time, the occupancy signal may notbe transmitted. The occupancy signal may be one of an implementationsignal that may be differently transmitted depending on implementationof a terminal, a signal in a preamble form (e.g., PRACH), and an SRSsignal.

Method 1 is a method in which a channel sensing operation for anunlicensed band in which uplink signal transmission is set is performedfor a fixed channel sensing period at a fixed point in time. Forexample, the channel sensing operation may be performed at a positionwhere the channel sensing operation may end immediately before startingof a first symbol transmitted in an uplink subframe in which the uplinksignal transmission is set, or the channel sensing operation may beperformed at a starting point in time of the last OFDM symbol in asubframe immediately before the uplink subframe in which the uplinksignal transmission is set. The channel occupancy signal may betransmitted immediately before starting of the first symbol transmittedin the uplink subframe in which the uplink signal transmission is set.Further, the channel sensing operation may be performed in the firstOFDM or SC-FDMA symbol in the uplink subframe in which the uplink signaltransmission is set.

The channel sensing operation may be performed at a position where thechannel sensing operation may end immediately before starting of asecond OFDM or SC-FDMS symbol in the uplink subframe, or the channelsensing operation may be performed at a starting point in time of thefirst OFDM or SC-FDMA symbol in a subframe of the uplink subframe inwhich the uplink signal transmission is set. The channel occupancysignal may be transmitted to immediately before starting of the secondsymbol transmitted in the uplink subframe in which the uplink signaltransmission is set.

With respect to Method 2, the LAA terminal of which uplink signaltransmission is set in an unlicensed band may perform a channel sensingoperation for the unlicensed band in which the uplink signaltransmission is set for a channel sensing period 535 that is set beforethe set uplink signal transmission. The channel sensing period 535 maybe randomly selected in a contention window of the LAA terminal or setby the base station. Further, the channel sensing period 535 may beconfigured of one fixed period 533 and one or more variable periods 537.The channel sensing period 535 may also be configured of the variableperiods 537 without the fixed period 533, or may also be configured ofonly one variable period.

Further, Method 2 is a method in which a channel sensing operation foran unlicensed band in which uplink signal transmission is set iscontinuously performed at a random point in time. For example, thechannel sensing operation may be performed at a position where thechannel sensing operation may end immediately before starting of a firstsymbol transmitted to the channel sensing period in an uplink subframein which the uplink signal transmission is set, or the channel sensingoperation may be performed at a starting point in time of the last OFDMsymbol in a subframe immediately before the uplink subframe in which theuplink signal transmission is set. At this point, the channel occupancysignal may be transmitted to immediately before starting of the firstsymbol transmitted in the uplink subframe in which the uplink signaltransmission is set.

Further, the channel sensing operation may be performed in the firstOFDM or SC-FDMA symbol in the uplink subframe in which the uplink signaltransmission is set. Further, the channel sensing operation may beperformed in the first OFDM or SC-FDMA symbol in the set uplinksubframe. The channel sensing operation may be performed at a positionwhere the channel sensing operation may end immediately before astarting of a second OFDM or SC-FDMS symbol in the uplink subframe, orthe channel sensing operation may be performed at a starting point intime of the first OFDM or SC-FDMA symbol in a subframe of the uplinksubframe in which the uplink signal transmission is set. The channeloccupancy signal may be transmitted to immediately before, starting ofthe second symbol transmitted in the uplink subframe in which the uplinksignal transmission is set.

The base station may inform of or provide a size of a contention windowof the LAA terminal, and the LAA terminal may randomly set a channelsensing period within the contention window. Information on the channelsensing period may be informed or provided to the terminal settinguplink transmission when the base station transmits uplink controlinformation of the terminal or may be informed to all terminals througha common downlink control channel.

The LAA terminal can have a preset contention window size and may use(or change) the contention window size in consideration of aretransmission scheduling related value (e.g., a new data indicator(NDI)) transmitted from the base station.

If a point in time when the channel sensing operation ends is earlierthan the set uplink signal transmission point in time, the terminal maytransmit an occupancy signal 550 for occupying the channel from thepoint in time when the channel sensing operation ends to the uplinksignal transmission point in time. At this point, if the channel sensingoperation ends immediately before the uplink signal transmission pointin time, the occupancy signal may not be transmitted. The occupancysignal may be one of an implementation signal that may be differentlytransmitted depending on implementation of a terminal, a signal in apreamble form (e.g., PRACH), and an sounding reference signal (SRS)signal.

With respect to Method 3, the LAA terminal of which uplink signaltransmission is set in an unlicensed band may perform the set uplinksignal transmission without a separate channel sensing operation beforethe set uplink signal transmission. Method 3 may be applied to a case inwhich after an LAA cell performs a channel sensing operation fordownlink transmission, the LAA cell occupying the channel sets uplinksignal transmission of an LAA terminal through a downlink controlchannel, and uplink transmission 510 of the LAA terminal is performedimmediately after downlink transmission 500 of the LAA cell ends, orending of the downlink transmission 500 of the LAA cell and starting ofthe uplink transmission 510 of the LAA terminal are performed within apredetermined time 505 (e.g., within 25 us).

At least one of the methods for a channel sensing operation (Method 1,Method 2, or Method 3) and a channel sensing period for the method maybe set to be different depending on whether a cell setting the uplinksignal transmission (or a cell scheduling uplink transmission) is alicensed band cell or an unlicensed band cell. If the cell setting theuplink signal transmission is an unlicensed band cell, at least one ofthe methods for a channel sensing operation and a channel sensing periodmay be set to be different depending on whether the cell setting theuplink signal transmission is the same unlicensed band cell as the cellin which the terminal performs uplink signal transmission, or anunlicensed band cell that is different from the cell in which the uplinksignal transmission is performed among unlicensed band cells. When theuplink signal transmission is set in an unlicensed band cell that isoperated in another spectrum that is different from a licensed band oran unlicensed band cell in which uplink signal transmission isperformed, the uplink channel sensing operation may be set to beperformed according to Method 2, and when the uplink signal transmissionis set in the same unlicensed band cell as the unlicensed band cell inwhich uplink signal transmission is performed, the uplink channelsensing operation may be set to be performed according to Method 1. Whenthe uplink signal transmission is set in an unlicensed band cell that isoperated in other spectrum that is different from a licensed band or anunlicensed band cell in which uplink signal transmission is performed, arequired length of a channel sensing operation period may be set to belonger than a required length of a channel sensing operation period whenthe uplink signal transmission is set in the same unlicensed band cellas the unlicensed band cell in which uplink signal transmission isperformed. In Method 2, a required minimum average length of a channelsensing operation period may be set to be different by differentlysetting a minimum value or a maximum value of a contention windowdepending on a cell in which the uplink signal transmission is set.

For example, in Method 1, a size of a channel sensing period (in a casein which a cell setting uplink signal transmission is a licensed bandcell, or in a case in which a cell setting uplink signal transmission isan unlicensed band cell that is different from an unlicensed cell inwhich uplink signal transmission is performed among unlicensed bandcells) may be set to be greater than or equal to that in a case in whicha cell setting uplink signal transmission is the same unlicensed bandcell as the unlicensed cell in which uplink signal transmission isperformed among unlicensed band cells. A size of a channel sensingperiod that is set to be different depending on a cell setting theuplink signal transmission may be set by a higher layer signal ordefined in advance. The size of the channel sensing period may be set tobe different depending on a set kind of uplink signal. A size of achannel sensing period in a case of transmitting an uplink signalincluding an uplink data channel may be set to be greater than or equalto that in a case of transmitting an uplink signal (e.g., uplink controlchannel, SRS, PRACH, etc.) that does not include an uplink data channel.

In Method 2, a size of a channel sensing period or a size of acontention window (in a case in which a cell setting uplink signaltransmission is a licensed band cell, or in a case in which a cellsetting uplink signal transmission is an unlicensed band cell that isdifferent from an unlicensed cell in which uplink signal transmission isperformed among unlicensed band cells) may be set to be greater than orequal to those in a case in which a cell setting uplink signaltransmission is the same unlicensed band cell as the unlicensed cell inwhich uplink signal transmission is performed among unlicensed bandcells. A size of a channel sensing period or a size of a contentionwindow that is set to be different depending on a cell setting theuplink signal transmission may be set by a higher layer signal ordefined in advance. The size of the channel sensing period or the sizeof the contention window may be set to be different depending on a setkind of uplink signal. For example, a size of a channel sensing periodor a size of a contention window in a case of transmitting an uplinksignal including an uplink data channel may be set to be greater than orequal to than those in a case of transmitting an uplink signal (e.g.,uplink control channel, SRS, PRACH, etc.) that does not include anuplink data channel.

The base station may differently set the uplink channel sensingoperation and at least one of relevant variable values depending on akind or characteristics of a cell setting uplink signal transmission(e.g., when a cell setting uplink signal transmission is a licensed bandcell, when a cell setting uplink signal transmission is an unlicensedband cell that is different from an unlicensed cell in which uplinksignal transmission is performed among unlicensed band cells, or when acell setting uplink signal transmission is the same unlicensed band cellas the unlicensed cell in which uplink signal transmission is performedamong unlicensed band cells), or depending on a kind or characteristicsof an uplink transmission signal of the terminal (e.g., in a case oftransmitting an uplink signal including an uplink data signal, or in acase of transmitting an uplink control signal or control channel withoutincluding an uplink data signal), and may perform a setting of the setchannel sensing operation and variable values for the terminal using ahigher layer signal. For example, in a case in which a cell settinguplink signal transmission is a licensed band cell, or in a case inwhich a cell setting uplink signal transmission is an unlicensed bandcell that is different from an unlicensed cell in which uplink signaltransmission is performed among unlicensed band cells, a channel sensingoperation using a variable period like Method 2 may be set or defined inadvance, and in a case in which a cell setting uplink signaltransmission is the same unlicensed band cell as the unlicensed cell inwhich uplink signal transmission is performed among unlicensed bandcells, a channel sensing operation using a fixed period like Method 1may be set or defined in advance.

The base station may perform a setting of a method for a channel sensingoperation for the terminal by including a field for setting a method(LBT type) for a channel sensing operation to be performed by theterminal in uplink transmission setting information of the terminal.

The base station may transmit the information on the channel sensingtype to the UE through a UL grant. The information on the channelsensing type may be information for setting whether to perform thechannel sensing operation using the fixed time period like the Method 1or whether to perform the channel sensing operation using the variabletime period like the Method 2.

Based on the information on the channel sensing type, the UE maytransmit the uplink signal to the base station after performing thechannel sensing operation during the fixed time period according to theMethod 1. In addition, based on the information on the channel sensingtype, the UE may transmit the uplink signal to the base station afterperforming the channel sensing operation during the variable time periodaccording to the Method 2. The variable time period may be randomly setbased on the contention window for the UE. For example, the variabletime period may be determined based on a randomly selected value and aminimum sensing slot in the contention window.

The terminal receiving the uplink transmission setting information mayperform a channel sensing operation for the set uplink unlicensed bandaccording to the method for a channel sensing operation (or LBT type)included in the information and instructed by the base station. Detailedinformation (e.g., a length of a channel sensing period, a size of acontention window, etc.) required for the channel sensing operation maybe defined in advance by the base station and the terminal, set by basestation for the terminal through a higher layer signal, or set for theterminal by being included in the uplink transmission settinginformation.

When the base station sets uplink transmission of the terminal, in acase in which information (e.g., a length of a channel sensing period,or a size of a contention window) required for a channel sensingoperation of the terminal is set for the terminal, if one or moreterminals are scheduled in a subframe in which the corresponding uplinktransmission is set, e.g., an uplink subframe n, the base station mayinform terminals of a length of a channel sensing period or a size of acontention window that is determined for each terminal through thechannel sensing operation, respectively, as the information required byone or more terminals of which uplink transmission is set in thesubframe n for a channel sensing operation (a length of a channelsensing period or a size of a contention window). When the terminalperforming the channel sensing operation in the subframe n, however,uses different lengths of a channel sensing period, or different sizesof a contention window to perform the channel sensing operation, ifthere is a terminal that ends first the channel sensing operation, andoccupies the channel to perform uplink transmission among the terminals,other terminals receiving an uplink signal transmitted by the terminalmay not properly perform a channel sensing operation. Accordingly, thebase station may inform each terminal of the same length of a channelsensing period or the same size of a contention window as theinformation (a length of a channel sensing period, or a size of acontention window) required by the one or more terminals of which uplinktransmission is set in the subframe n for a channel sensing operation,respectively. In determining the same length of a channel sensing periodor the same size of a contention window, the base station may select amaximum value of lengths of a channel sensing period or sizes of acontention window that are determined for each terminal of which uplinktransmission is set in the subframe n, and the base station may informthe terminals performing uplink transmission in the subframe n of themaximum value. As another method, the base station may also perform asetting so that the terminals having the same value among lengths of achannel sensing period or sizes of a contention window that aredetermined for respective terminals of which uplink transmission is setin the subframe n perform uplink transmission in the subframe n.

Further, the base station selects a value to be used in the subframe namong lengths of a channel sensing period or sizes of a contentionwindow that are determined for respective terminals of which uplinktransmission is set in the subframe n. The base station also calculatesa position and the number of symbols excluded from uplink transmissionin the uplink subframe n, or a position of a start symbol and a positionof an end symbol in which uplink transmission is actually performed inthe uplink subframe n, based on the selected length of a channel sensingperiod or the selected size of a contention window. Even in a case inwhich the base station differently informs respective terminals of alength of a channel sensing period or a size of a contention window, atleast one of a position of a start symbol and a position of an endsymbol in which uplink transmission is actually performed in the uplinksubframe n needs to be identically set for the terminals performinguplink transmission in the uplink subframe n. If an uplink transmissionstarting point in time of one or more terminals is different in theuplink subframe n, other terminals receiving an uplink signaltransmitted by the terminal may not properly perform a channel sensingoperation.

Accordingly, the base station may calculate a time required for anuplink channel sensing operation in the subframe n based on at least oneof a length of a channel sensing period or a size of a contention windowthat is determined for each terminal of which uplink transmission is setin the subframe n, e.g., based on at least one of a maximum size of acontention window, an average length of a channel sensing period thatmay be selected from the maximum size of a contention window, a maximumaverage size of a contention window, and an average length of a channelsensing period that may be selected from the maximum average size of acontention window of terminals intending to setting uplink transmissionin the subframe n. The base station may also identically inform theterminals performing uplink transmission of an uplink transmission startsymbol or an uplink transmission starting point in time, and an uplinktransmission end symbol or an uplink transmission ending point in timein the subframe n based thereon.

The base station may select terminals having at least one same value ofa maximum size of a contention window, an average length of a channelsensing period that may be selected from the maximum size of acontention window, a maximum average size of a contention window, and anaverage length of a channel sensing period that may be selected from themaximum average size of a contention window as the terminals settinguplink transmission in the subframe n to calculate a time required foran uplink channel sensing operation in the subframe n. The base stationmay also inform the terminals performing uplink transmission of anuplink transmission start symbol or an uplink transmission startingpoint in time, and an uplink transmission end symbol or an uplinktransmission ending point in time in the subframe n based thereon.

Further, the terminal can be configured so that uplink signaltransmission in N uplink subframes (multi-subframe scheduling) may beperformed as one uplink transmission setting information that istransmitted from the base station in a subframe n for the uplink signaltransmission of the terminal in a downlink control channel of at leastone of a licensed band cell, an unlicensed band cell different from theuplink transmission cell, and the same unlicensed band cell as theuplink transmission cell that includes a subframe n+K. A method for achannel sensing operation that is performed before transmission in oneset subframe or a plurality of set uplink subframes (or UL burst) startsand a method for a channel sensing operation that is performed by theterminal occupying the uplink channel in the occupied uplink subframemay be different from each other. For example, in a terminal configuredso that uplink signal transmission in N uplink subframes (multi-subframescheduling) may be performed as one uplink transmission settinginformation that is transmitted from the base station in a subframe nfor the uplink signal transmission of the terminal that includes asubframe n+K, the channel sensing operation performed before the setuplink subframe (or UL burst) transmission starts may be performedaccording to a channel sensing method having a variable period linkMethod 2. The channel sensing operation performed by the terminaloccupying an uplink channel by performing the channel sensing operationaccording to Method 2 in the plurality of set uplink subframes may beperformed according to a channel sensing method having a fixed channelsensing period like Method 1. A required minimum average length of achannel sensing period of a channel sensing operation (Method 1)performed in the plurality of set uplink subframes may be set to beshorter than that of a channel sensing operation (Method 2) performedbefore the set uplink subframe (or UL burst) transmission starts.

Further, in the terminal configured so that uplink signal transmissionin N uplink subframes (multi-subframe scheduling) may be performed asone uplink transmission setting information that is transmitted from thebase station in a subframe n for the uplink signal transmission of theterminal in a downlink control channel of at least one of a licensedband cell, an unlicensed band cell different from the uplinktransmission cell, and the same unlicensed band cell as the uplinktransmission cell includes a subframe n+K. A method for a channelsensing operation that is performed before transmission in one setsubframe or a plurality of set uplink subframes (or UL burst) starts anda method for a channel sensing operation that is performed by theterminal occupying the uplink channel in the occupied uplink subframemay be identical to each other. For example, when a terminal 1configured so that uplink signal transmission in N uplink subframes(multi-subframe scheduling) may be performed as one uplink transmissionsetting information that is transmitted from the base station in asubframe n for the uplink signal transmission of the terminal includes asubframe n+K as described above, and a terminal 2 configured so thatuplink signal transmission in some uplink subframes (M<N) among the Nuplink subframes may be performed coexist, since a channel sensingoperation of the terminal 2 exists in an uplink subframe transmissionperiod of the terminal 1, the terminal 2 may be configured to performthe same channel sensing operation as the channel sensing operationperformed by the terminal 1 in the plurality of set uplink subframe. Inother words, in the terminal configured so that uplink signaltransmission in N uplink subframes (multi-subframe scheduling) may beperformed as one uplink transmission setting information that istransmitted from the base station in a subframe n for the uplink signaltransmission of the terminal in a downlink control channel of at leastone of a licensed band cell, an unlicensed band cell different from theuplink transmission cell, and the same unlicensed band cell as theuplink transmission cell includes a subframe n+K, a channel sensingoperation is performed for starting the set uplink transmissionaccording to a method (LBT type) for a channel sensing operationincluded in the uplink transmission setting. In the N uplink subframetransmission periods, a method for a channel sensing operation that isthe same as the method for a channel sensing operation included in theuplink transmission setting may be performed, or a method for a channelsensing operation that is different from the method for a channelsensing operation included in the uplink transmission setting may beperformed. When a method for a channel sensing operation that isdifferent from the method for a channel sensing operation included inthe uplink transmission setting is performed, the method for a channelsensing operation performed in the N uplink subframe transmissionperiods may be defined in advance by the base station and the terminal,set by the base station for the terminal through a higher layer signal,or set by the base station for the terminal by adding a field forsetting the method for a channel sensing operation to the uplinktransmission setting information.

Operations for Method 2 will now be described.

The base station may set a channel sensing period for uplink signaltransmission of the terminal through a downlink control channel for theterminal. The channel sensing period may be configured of a fixed periodand/or a variable period, and the variable period may be randomlyselected in an uplink contention window of the base station.Accordingly, the channel sensing period may vary depending on a lengthof a randomly selected variable period (in other words, the number ofthe back-off counter). Therefore, the channel sensing period set by thebase station for the terminal can be a length of the variable period orthe number of the back-off counter. A total channel sensing periodrequired by the terminal for an uplink channel sensing operationincludes a fixed period and a variable period set by the base station.

As described above, in order to set a channel sensing period requiredfor an uplink channel sensing operation of the terminal, the basestation needs to set a contention window. A method for setting, by thebase station, a contention window for an uplink channel sensingoperation can include the base station determining a reference subframebefore a channel sensing period setting point in time for a channelsensing operation according to a result of uplink data channel receptionof the terminal that is received before the base station sets a channelsensing period required for uplink channel sensing operation for theterminal. The base station can also set a contention window according toan uplink data channel reception result transmitted from the terminal inthe reference subframe.

FIG. 6 is a diagram illustrating a method for setting the contentionwindow and a channel sensing period, according to an embodiment of thepresent disclosure.

Method 2-1: The base station defines a first uplink subframe 620 in alatest uplink transmission period 638 that is set before a channelsensing period setting point in time 680 for an uplink channel sensingoperation 650 of the terminal as a reference subframe. The base stationincreases a contention window when Z% or more of NACK of the uplink datachannel reception result 660 transmitted from the terminal in thereference subframe is generated.

Method 2-2: The base station increases a contention window when Z% ormore of NACK of the uplink data channel reception results 660 and 662(which is received from the terminal determined before the channelsensing period setting point in time 680 for the uplink channel sensingoperation 650 of the terminal in the latest uplink transmission period638 that is set before the channel sensing period setting point in time680 for the uplink channel sensing operation 650) is generated.

Method 2-3: The base station increases a contention window when Z% ormore of NACK of the uplink data channel reception result 662 (which isin an uplink subframe that is most recently determined before thechannel sensing period setting point in time 680 for the uplink channelsensing operation 650 of the terminal) is generated.

If Z% or more of NACK of the uplink data channel reception result, whichis transmitted from the terminal in the reference subframe used forchanging a contention window in Methods 2-1, 2-2, and 2-3 is notgenerated, it is possible to decrease or initialize the contentionwindow. Z may be defined in advance by the base station and theterminal, or set by the base station for the terminal through a higherlayer signal as a value of 10, 20, 50, 80, or 100%. The Z value may bedefined to be different according to a regulation for each region oreach frequency spectrum. Further, the Z value may be set to be differentdepending on whether a cell setting uplink signal transmission (or acell scheduling uplink transmission) is a licensed band cell or anunlicensed band cell. In other words, if the cell setting the uplinksignal transmission is an unlicensed band cell, the Z value may be setto be different depending on whether the cell setting the uplink signaltransmission is the same unlicensed band cell as the cell in which theterminal performs uplink signal transmission, or an unlicensed band cellthat is different from the cell in which the uplink signal transmissionis performed among unlicensed band cells. For example, when the uplinksignal transmission is set in an unlicensed band cell that is operatedin another spectrum that is different from a licensed band or anunlicensed band cell in which uplink signal transmission is performed,Z% is set to be low as compared to a case in which the uplink signaltransmission is set in the same unlicensed band cell as the unlicensedband cell in which uplink signal transmission is performed, therebymaking it possible to differently set a probability with which acontention window is changed, depending on whether a channel sensingoperation for the unlicensed band is performed.

Further, a contention window may be increased by at least one of anexponential increase method, a linear increase method, and a method ofincreasing within a contention window set that is defined in advance.Moreover, an uplink data channel transmission result used once forsetting a contention window as a reference subframe may not be used forsetting other contention windows. Additionally, although the basestation configures uplink transmission for an unlicensed band through alicensed band downlink, in a case in which it is determined that uplinktransmission received from the terminal configuring the uplinktransmission is determined as DTX, if the uplink transmission determinedas DTS as described above is included in a reference subframe, theuplink transmission result may not be reflected in criteria for changinga contention window. Although the base station configures uplinktransmission for an unlicensed band through unlicensed band downlink, ina case in which it is determined that uplink transmission received fromthe terminal configuring the uplink transmission is determined as DTX,if the uplink transmission determined as DTS as described above isincluded in a reference subframe, the uplink transmission result may bedetermined as NACK and included in criteria for changing a contentionwindow. If the base station determines that the uplink transmissionresult of the terminal is NACK/DTX, any state, etc., the uplinktransmission result may be determined as NACK and included in criteriafor changing a contention window.

A reference subframe that is actually applied in changing a contentionwindow in Methods 2-1, 2-2, and 2-3 may be different depending on apoint in time when uplink data channel reception result transmitted fromthe terminal in the reference subframe is determined. In other words, apoint in time when uplink data channel reception result transmitted fromthe terminal in the reference subframe is determined as ACK/NACK may bedifferent for each base station.

For example, in FIG. 6, the base station 1 may determine in a subframen+6 an uplink data channel reception result transmitted from theterminal in a subframe n+4, and another base station 2 may determine ina subframe n+7 an uplink data channel reception result transmitted fromthe terminal in the subframe n+4. To solve the above problem, thereference subframe may be defined as a reference subframe that is validafter a predetermined time base on a point in time when the terminaltransmits an uplink data channel. For example, an uplink data channelreception result transmitted from the terminal in the subframe n+4 maybe determined as valid after a subframe n+K (e.g., K=3 or 4), and acontention window may be increased by using one of Methods 2-1, 2-2, and2-3 when N% or more of NACK of the uplink data channel reception resulttransmitted from the terminal in the valid reference subframe isgenerated. If it is assumed that K=3 (even when the base stationdetermines at 666 in a subframe n+9 a transmission result of an uplinkdata channel 626 transmitted by the terminal in a subframe n+7) the basestation may not include the transmission result of the uplink datachannel 626 transmitted in the subframe n+7 that does not satisfy thecondition that K=3 in a reference subframe at a channel sensing periodsetting point in time n+10 for an uplink channel sensing operation 650of the terminal, in Method 2-2. The reference subframe in Method 2-2 isuplink subframes 620, 622, and 624. As another example, if it is assumedthat K=3 (even when the base station determines at 666 in a subframe n+9a transmission result of an uplink data channel 626 transmitted by theterminal in a subframe n+7) the base station determines the latestuplink subframe 624 satisfying the condition that K=3 as a referencesubframe for an uplink channel sensing operation 650 of the terminal, inMethod 2-3.

The base station may set a size of a contention window for determiningan uplink channel sensing period by at least one of Methods 2-1, 2-2,and 2-3. The base station may use a plurality of contention windowscorresponding to respective terminals for each terminal, or may use onecontention window capable of being applied to all terminals. The basestation may use a plurality of contention windows depending on a qualityof service (QoS) or LBT class, or may apply a contention window set tobe different for each QoS or LBT class to all terminals.

When the base station uses one contention window capable of beingapplied to all terminals (or cell-specific contention window), the basestation may set a size of a contention window for an uplink channelsensing operation according to the determination result by at least oneof Methods 2-1, 2-2, and 2-3. When the base station uses a plurality ofcontention windows depending on a QoS or LBT class (or cell-specificcontention window per LBT class), the base station may set a pluralityof contention windows together according to the determination result byat least one of Methods 2-1, 2-2, and 2-3. For example, when it isdetermined by the base station using a contention window 1 for LBT class1 and a contention window 2 for LBT class 2 that the contention windowneeds to be changed by at least one of Methods 2-1, 2-2, and 2-3, boththe contention window and the contention window 2 may be increased orinitialized together. In a case in which the base station uses aplurality of contention windows depending on LBT class, the base stationmay select an LBT class corresponding to the uplink transmission period,select a random variable (or backoff counter) within a contention windowfor the selected LBT class, and set the selected variable as theselected channel sensing period value (or selected variable value) forthe terminal requiring an uplink channel sensing operation.

The randomly selected channel sensing period value may be commonlyapplied to all cases requiring an uplink channel sensing operation inthe uplink transmission period. For example, in order to perform achannel sensing operation for an LBT class in the uplink transmissionperiod 658 in FIG. 6, the base station may select a random variablewithin a contention window for the selected LBT class, and set theselected channel sensing period value for the terminal configuringuplink transmission in a period 658 so that the selected channel sensingperiod value is commonly used for uplink channel sensing operations 650,652, 654, and 656. In other words, the base station may set one channelsensing period value for one uplink transmission period, and use the setchannel sensing period value for all uplink channel sensing operationswithin the uplink transmission period. The base station may set and usea channel sensing period value for each uplink channel sensingoperations within the uplink transmission period. The channel sensingperiod may be selected within a contention window for the selected LBTclass. In other words, different channel sensing period values may beselected within one contention period and applied to uplink channelsensing periods 650, 652, 654, and 656.

When the base station uses a plurality of contention windowscorresponding to respective terminals for each terminal (or UE-specificcontention window), the base station may set contention windows ofterminals performing uplink signal transmission in an uplinktransmission period 638 in FIG. 6 including a reference subframe ofMethod 2-1, 2-2, or 2-3 according to an uplink transmission result ofthe terminal determined by at least one of Methods 2-1, 2-2, and 2-3. Inother words, contention windows of terminals that did not perform uplinksignal transmission in the uplink transmission period 638 including areference subframe of Method 2-1, 2-2, or 2-3 maintains previously setcontention windows without being changed. The base station may also setcontention windows of all terminals regardless of whether the uplinksignal transmission is performed in an uplink transmission period 638including a reference subframe of Method 2-1, 2-2, or 2-3 according to aresult determined by at least one of Methods 2-1, 2-2, and 2-3.

In the case in which the base station uses a plurality of contentionwindows corresponding to respective terminals for each terminal, achannel sensing period required for an uplink channel sensing operationmay be set by using contention windows of the terminals that are set sothat the uplink channel sensing operations are performed at the samepoint in time.

Referring again to FIG. 6, for example, the base station may select arandom variable (or backoff counter) based on a largest contentionwindow of contention windows of terminals configuring uplinktransmission 640 in a subframe n+14, and set a channel sensing periodvalue (or selected variable value) required for the uplink channelsensing operation 650 for the terminals configuring the uplinktransmission 640 in the subframe n+14 using the selected variable.Alternatively, the base station may select a random variable (or backoffcounter) within respective contention windows of terminals configuringuplink transmission 640 in a subframe n+14, and may select a largestchannel sensing period or backoff counter of the selected variables as achannel sensing period value required for the uplink channel sensingoperation 650 to set the channel sensing period value required for theuplink channel sensing operation 650 for the terminals configuring theuplink transmission 640 in the subframe n+14.

The base station may set the selected channel sensing period for theterminal through a downlink control channel. The selected channelsensing period value (or backoff counter) may be set for the terminal bybeing included in control information (DCI) for the uplink data channelor uplink control signal transmission configuration of the terminal. Afield corresponding to a channel sensing period value may be set to DCIformat 0, 4 or a new DCI format in addition to variables associated withuplink transmission and transmitted to the terminal requiring uplinktransmission setting. At this point, the selected channel sensing periodvalue may also be transmitted to all terminal by using a common searchspace of a downlink control channel.

Unlike Method 2, the base station transmits a result of uplink signaltransmission of the terminal for each terminal, the terminal sets acontention window based on the uplink signal transmission result, and achannel sensing period for a channel sensing operation for uplinktransmission set using the set contention window may be set. In otherwords, when it is set in uplink signal setting information of theterminal transmitted by the base station through a downlink controlchannel that a base station reception result for previous uplink signaltransmission is NACK, the terminal may increase the contention window.When it is set in uplink signal setting information of the terminaltransmitted by the base station through a downlink control channel thata base station reception result for previous uplink signal transmissionis ACK, the terminal may initialize the contention window.

When it is determined that a base station reception result for previousuplink transmission is NACK regardless of hybrid automatic repeatrequest (HARQ) process for the uplink transmission, the terminal mayincrease the contention window and select a channel sensing period valuewithin the increased contention window. The terminal may divide and usethe contention window for each HARQ process for the uplink transmission.If the set uplink transmission is set as an HARQ process that isdifferent from an HARQ process for previous uplink transmission, theterminal may select a channel sensing period using a contention windowcorresponding to the set HARQ process regardless of the base stationreception result for the previous uplink transmission. When a basestation reception result for previous uplink transmission is NACK, acontention window for the previous uplink transmission is increased. Ina case in which the terminal divides and uses a contention window foreach uplink HARQ process, the terminal may also select a channel sensingperiod value based on a largest contention window of contention windowsof the set HARQ process.

FIG. 7 is a flowchart of a method for setting a contention window in abase station for a channel sensing operation, according to an embodimentof the present disclosure.

In step 701, contention window setting criteria is set. The entireuplink transmission period of the terminal or a part of the uplinktransmission period of the terminal among uplink transmission periodsbefore setting a channel sensing period for an uplink channel sensingoperation may be set as a reference subframe for setting a contentionwindow. The base station may use a reception result of uplinktransmission of the terminal in the reference subframe that isdetermined before setting the channel sensing period for the uplinkchannel sensing operation.

In step 702, a contention window setting reference terminal is set. Aterminal performing transmission in the entire or some subframes of theuplink transmission period may be set as a reference terminal.

In step 703, a contention window changing method is set. That is, thecontention window may be changed using a ratio of NACK of an uplinksignal reception result determined according to the steps 701 and 702.

In step 704, the base station receives an uplink signal from theterminal. In step 705, a reception result of the uplink signal of theterminal received in step 704 is determined. In step 706, a contentionwindow is set by determining the uplink reception result of the terminalthat is determined in step 705 based on the contention window changingcriteria set in steps 701, 702 and 703.

If it is determined in step 706 that the contention window needs to beincreased, the base station increases the contention window, sets achannel sensing period for an uplink channel sensing operation withinthe increased contention window, and sets the selected channel sensingperiod for the terminal by including the channel sensing period inuplink transmission setting information in step 707. If it is determinedin step 706 that the contention window does not need to be increased,the base station initializes the contention window, sets a channelsensing period for an uplink channel sensing operation within theinitialized contention window, and sets the selected channel sensingperiod for the terminal by including the channel sensing period inuplink transmission setting information in step 708.

FIG. 8 is a flowchart of a method for setting a contention window in aUE for a channel sensing operation, according to an embodiment of thepresent disclosure.

In step 801, the terminal receives configuration information for uplinksignal transmission from the base station. A channel sensing period maybe included in the uplink signal transmission setting information. Theterminal receiving the channel sensing period from the base station instep 802 senses a channel during the channel sensing period beforeuplink signal transmission set in step 803.

If it is determined in step 804 that the channel sensed in step 803 isin an idle state, the terminal performs the set uplink signaltransmission in step 805. If it is determined in step 804 that thechannel sensed in step 803 is being occupied by other devices, theterminal does not perform the uplink signal transmission in step 806.

FIG. 9 is a diagram illustrating a base station apparatus for setting acontention window and a channel sensing period of the terminal by thebase station using an unlicensed band, according to an embodiment of thepresent disclosure.

A receiver 920 of the base station may perform an operation for sensingan unlicensed band channel using a set value for a channel sensingoperation set through a controller 900 of the base station, as well as afunction of receiving a signal from the base station or the terminal, ormeasuring a channel from the base station or the terminal. Further, thecontroller 900 of the base station may determine a reception result ofthe signal received from the terminal through the receiver 920 of thebase station, set a contention window required for a channel sensingoperation of the terminal according to the determination result, and seta channel sensing period value of the terminal by selecting a randomvariable within the set contention window. Further, the controller 900of the base station may transmit a control signal configuring uplinksignal transmission of the terminal through a downlink control channelby including the set channel sensing period value of the terminal in atransmitter 910 of the base station.

FIG. 10 is a diagram illustrating a terminal apparatus using anunlicensed band, according to an embodiment of the present disclosure.

A controller 100 of the terminal in FIG. 10 may set a channel sensingoperation so that the terminal performs the channel sensing operationduring a channel sensing period required for uplink signal transmissionin an unlicensed band that is set by the base station using a receiver1020. Further, the controller 1000 may configure uplink transmission intime and frequency resources set according to uplink signal transmissionset by the base station and received through the receiver 1020.

The receiver 1020 senses a channel during the channel sensing period setby the controller 1000, and when it is determined by the controller 1000that the channel is in an idle state based on intensity of a signalreceived by the receiver during the channel sensing period, atransmitter 1010 may configure uplink transmission in time and frequencyresources set according to the uplink signal transmission set by thebase station.

While the present disclosure has been shown and described with referenceto certain embodiments thereof, it will be understood by those skilledin the art that various changes in form and details may be made thereinwithout departing from the scope of the present disclosure. Therefore,the scope of the present disclosure should not be defined as beinglimited to the embodiments, but should be defined by the appended claimsand equivalents thereof.

What is claimed is:
 1. A base station for transmitting information in awireless communication system, the base station comprising: atransceiver; and a controller coupled with the transceiver andconfigured to control to: generate information on a channel sensingoperation of a user equipment (UE) in an unlicensed band, wherein theinformation on the channel sensing operation indicates one of a firsttype performing the channel sensing operation using a variable timeperiod, a second type performing the channel sensing operation using afixed time period, and a third type not performing the channel sensingoperation, and transmit, to the UE, the information on the channelsensing operation.
 2. The base station of claim 1, wherein theinformation on the channel sensing operation indicates the third type incase that a gap from an end of a downlink (DL) transmission to abeginning of a uplink (UL) transmission is not greater than apredetermined time.
 3. The base station of claim 1, wherein an uplinksignal is transmitted after sensing a channel for the unlicensed bandduring the variable time period in case that the information on thechannel sensing operation indicates the first type, and wherein theuplink signal is transmitted after sensing the channel for theunlicensed band during the fixed time period in case that theinformation on the channel sensing operation indicates the second type.4. The base station of claim 1, wherein the variable time period for thefirst type is randomly selected based on a contention window for the UE.5. The base station of claim 4, wherein a value of the contention windowis determined based on a new data indicator (NDI) value for a hybridautomatic repeat request (HARQ) process.
 6. A method for transmittinginformation by a base station in a wireless communication system, themethod comprising: generating information on a channel sensing operationof a user equipment (UE) in an unlicensed band, wherein the informationon the channel sensing operation indicates one of a first typeperforming the channel sensing operation using a variable time period, asecond type performing the channel sensing operation using a fixed timeperiod, and a third type not performing the channel sensing operation;and transmitting, to the UE, the information on the channel sensingoperation.
 7. The method of claim 6, wherein the information on thechannel sensing operation indicates the third type in case that a gapfrom an end of a downlink (DL) transmission to a beginning of a uplink(UL) transmission is not greater than a predetermined time.
 8. Themethod of claim 6, wherein an uplink signal is transmitted after sensinga channel for the unlicensed band during the variable time period incase that the information on the channel sensing operation indicates thefirst type, and wherein the uplink signal is transmitted after sensingthe channel for the unlicensed band during the fixed time period in casethat the information on the channel sensing operation indicates thesecond type.
 9. The method of claim 6, wherein the variable time periodfor the first type is randomly selected based on a contention window forthe UE.
 10. The method of claim 9, wherein a value of the contentionwindow is determined based on a new data indicator (NDI) value for ahybrid automatic repeat request (HARQ) process.
 11. A user equipment(UE) for receiving information in a wireless communication system, theUE comprising: a transceiver; and a controller coupled with thetransceiver and configured to control to: receive, from a base station,information on a channel sensing operation of the UE in an unlicensedband, wherein the information on the channel sensing operation indicatesone of a first type performing the channel sensing operation using avariable time period, a second type performing the channel sensingoperation using a fixed time period, and a third type not performing thechannel sensing operation, and transmit an uplink signal based on theinformation on the channel sensing operation.
 12. The UE of claim 11,wherein the information on the channel sensing operation indicates thethird type in case that a gap from an end of a downlink (DL)transmission to a beginning of a uplink (UL) transmission is not greaterthan a predetermined time.
 13. The UE of claim 11, wherein thecontroller is configured to: transmit the uplink signal after sensing achannel for the unlicensed band during the variable time period in casethat the information on the channel sensing operation indicates thefirst type, and transmit the uplink signal after sensing the channel forthe unlicensed band during the fixed time period in case that theinformation on the channel sensing operation indicates the second type.14. The UE of claim 11, wherein the variable time period for the firsttype is randomly selected based on a contention window for the UE. 15.The UE of claim 14, wherein a value of the contention window isdetermined based on a new data indicator (NDI) value for a hybridautomatic repeat request (HARQ) process.
 16. A method for receivinginformation by a user equipment (UE) in a wireless communication system,the method comprising: receiving, from a base station, information on achannel sensing operation of the UE in an unlicensed band, wherein theinformation on the channel sensing operation indicates one of a firsttype performing the channel sensing operation using a variable timeperiod, a second type performing the channel sensing operation using afixed time period, and a third type not performing the channel sensingoperation; and transmitting an uplink signal based on the information onthe channel sensing operation.
 17. The method of claim 16, wherein theinformation on the channel sensing operation indicates the third type incase that a gap from an end of a downlink (DL) transmission to abeginning of a uplink (UL) transmission is not greater than apredetermined time.
 18. The method of claim 16, further comprising:transmitting the uplink signal after sensing a channel for theunlicensed band during the variable time period in case that theinformation on the channel sensing operation indicates the first type;and transmitting the uplink signal after sensing the channel for theunlicensed band during the fixed time period in case that theinformation on the channel sensing operation indicates the second type.19. The method of claim 16, wherein the variable time period for thefirst type is randomly selected based on a contention window for the UE.20. The method of claim 19, wherein a value of the contention window isdetermined based on a new data indicator (NDI) value for a hybridautomatic repeat request (HARQ) process.